Hose pump



Aug- 26, 1 69 s. F. E. MEYER 3,453,092

HOSE PUMP Filed July 31, 196 7 9 Sheets-Sheet 1 Aug. 26, 1969 s. F. E. MEYER HOSE PUMP Filed July 31, 1967 9 Sheets-Sheet 2 WMU 121W WE Aug. 26, 1969 s. F. E. MEYER ,,3, 6

HOSE PUMP I Filed July 31. 1967 9 Sheets-Sheet 5 tzwf w BY CW n/ KM Aug. 26, 1969 s. F. E. MEYER HOSE PUMP 9 Sheets-Sheet 4 Filed July 31. 1967 R m m m ,JW ,wmmm

Aug. 26, 1969 s. F. E. MEYER HOSE PUMP 9 Sheets-Sheet Filed July 31. 1967 FIG. 11

INVENTOR Aug. 26, 1969 s. F. E. MEYER HOSE PUMP 9 Sheets-Sheet 6 Filed July 31, 1967 m m m m Aug. 26, 1969 s. F. E. MEYER HOSE PUMP 9 Sheets-Sheet '7 Filed July 31. 1967 IN ENTOR Aug. 26, 1969 s. F. MEYER HOSE PUMP 9 Sheets-Sheet 8 Filed July 31. 1967 1 N V EN TOR Aug. 26, 1969 s. F. E. MEYER 3,463,092

HOSE PUMP Filed July 31. 1967 9 Sheets-Sheet 9 FIG. 23

A x 100 \F,

INVENTOR.

United States Patent 3,463,092 HOSE PUMP Sven Fredrik Erhard Meyer, Stockholm, Sweden, assignor to Biotec AB, Stockholm, Sweden, a corporation of Sweden Filed July 31, 1967, Ser. No. 657,381 Claims priority, application Sweden, Aug. 1, 1966, 10,439/ 66 Int. Cl. F04!) 43/08 US. Cl. 103-149 19 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a hose pump of the type in which a flexible elastic hose is laid around a number of rollers rotatably mounted on a rotatable member. The rollers form relatively sharp bends in the hose, thereby forming closed cells within the hose, which cells are moved along the hose by the rotation of the rotatable member. According to the invention the rollers are adjustable radially on the rotatable member to change the length of the cells and thereby the liquid output of the pump at an unchanged rotational speed of the rotatable member. The invention further comprises mechanical means for the adjustment of the rollers on the rotatable member and for compensating for the variations of the length of the hose engaged by the rollers.

This invention refers to a hose pump, especially for medical use.

In a known type of hose pumps the flexible hose is led along a fixed, circular arcuate support and squeezed at equally spaced points by rollers, which are mounted on a rotatable member, so that upon rotation of the member peristaltic motions, i.e. wandering squeezings and widenings of the hose produce the desired pumping effect.

Instead of squeezing the hose against a circular arcuate support it has lately been suggested to place the hose around a number of rollers mounted on a rotatable member under a tension, which produces a flattening of the hose at those places where it is bent around the rollers with a small bending radius.

In all the hose pumps hitherto known it has been necessary for variating the pump output to change the speed of rotation of the rotatable member. Mechanical speed variators are complicated and onerous and do not permit a continuous and exact regualtion of the speed and thereby of the output of the pump from zero to a maximum.

The invention has the purpose to eliminate this difficulty and to provide a device permitting a variation of the output of the pump without changing the number of revolutions of the rotatable member.

The invention thus concerns a hose pump with a flexible and elastic hose placed under tension around a number of rollers rotatably mounted on a rotatable member and is characterized in that the rollers are adjustable on the rotatable member for simultaneously changing their radial distance from the axis of rotation of the rotatable member.

Thereby it becomes possible to continuously change the liquid volume enclosed in the hose between two rollers and when the rollers are adjusted to a least possible radius come suificiently near each other, the output will be adjustable from zero upwards. Instead of providing for the possibility to adjust the rollers sufficiently near to each other to form a countinuous bend in the hose and no more cells enclosed in the hose between separate bends, it is also possible to obtain the same effect by providing between the rollers, when adjusted on their minimum radius, supporting members forming a continuous bend on the hose and thereby a complete suppression of the pump output. The radial adjustment of the rollers on the rotatable member can be obtained in different ways, e.g. by mounting them on discs or arms, which are rotatably mounted on the rotatable member and which are simultaneously rotatable equal angles by means of a common driving member, e.g. a central gear wheel meshing with gear wheels connected with the discs or arms Other means for the radial adjustment of the rollers and for reducing the output of the pump to zero as well as further characteristics, details and advantages of the invention will become clear from the following description.

In the drawings:

FIG. 1 shows a longitudinal section through the rotatable member of a hose pump according to a first embodiment of the invention.

FIGS. 2 and 3 are axial projections of this embodiment at different adjustments of the rollers.

FIG. 4 shows an axial section through a second embodiment of the invention.

FIGS. 5 and 6 are axial views of the same embodiment in two different functional positions.

FIG. 7 shows a section through a third embodiment of the invention.

FIGS. 8 and 9 are axial views of the same embodiment in two different functional positions.

FIG. 10 is a side view of a fourth embodiment of a hose pump according to the invention.

FIG. 11 is an axial end view of the same embodiment.

FIG. 12 shows a longitudinal section and FIG. 13 a cross. section of this fourth embodiment in one functional position.

FIG. 14 shows a longitudinal section and FIG. 15 a cross section of this fourth embodiment in another functional position.

FIG. 16 is an axial view of a fifth embodiment shown in axial view in one functional position in FIG. 17 and in another functional position in FIG. 18.

FIG. 19 shows in a plan view and FIG. 20 in side elevation a sixth embodiment of the invention formed as a differential pump.

FIG. 21 shows a plan view and FIG. 22 a side view of a seventh embodiment of the invention, even this formed as a differential pump.

FIG. 23 shows a vertical axial section through a device for compensating for the pressure pulsations on the outlet side of the pump.

In the embodiment according to FIG. 1 the pump consists of a circular disc 1, which is fixedly mounted on the output shaft 2 of a motor (not illustrated) with highly reduced speed. On the disc are rotatably mounted a number of gear wheels 3 in circular arrangement. These gear wheels mesh with a central gear wheel 4 rotatably mounted on the shaft 2 and connected by means of a hub 5 with a covering plate '6 of preferably transparent material permitting the surveyance of the function of the pump. On each gear wheel 3, between this and the covering plate 6, is pivotally mounted a roller 7. The shaft 2, about which the central gear wheel 4, the hub 5 and the cover plate 6 are rotatable as a unit, extends past the cover plate -6 and is at its outer end fixedly connected to an outer plate 8, which is preferably also of transparent material to permit the surveyance of the function of the pump. The cover plate 6 bears near its periphery an axially extending, screw-threaded pin 9, extending through an arched slot 10 in the outer plate 8. 0n the periphery of one of the plates 6 and 8, e.g. of the cover plate 6, there is an index mark cooperating with a scale 11 along the periphery of the other plate e.g. plate 8. On the outside of the outer plate 8 a serrated nut 12 is screwed on the pin 9. The outer gear wheels, which form planet wheels in the planet gear mechanism formed by the gears 3 and 4, in which gear 4 is the sun wheel are so mounted, that all the rollers 7 have the same angular position relative to the radius passing through the axis of the respective planet wheel 3 and the central axis 2. The smaller rollers 13 shown besides the rollers 7 on each planet wheel 3 have an arrangement and a purpose to be described later on.

A hose, which from a connection for the pump is placed under tension between the disc 1 and the plate 6 over the outsides of the rollers 7 and back to a second connection preferably near the first one, will normally be bent over the rollers 7 in such manner, that it is flattened at its bends over the rollers but between the rollers resumes its normal cross sectional shape, whereby separate pumping cells are formed within the hose according to the principles known for all kinds of hose pumps. If the nut 12 is so loosened and the plates 6 and 8 are rotated relative to each other, the sun wheel 4 is turned relative to the disc 1 in a corresponding manner, whereby the planet Wheels 3 are rotated and the positions of the rollers 7 relative to the disc 1 are changed. In this manner the rollers can be adjusted to different radial distances from the shaft 2, which changes the size of the cells enclosed in the hose between the rollers.

The small rollers 13 are mounted on the planet wheels 3 in such positions, that upon adjustment of the planet wheels 3 with the rollers 7 at a small radial distance from the shaft 2 they add themselves to the supporting surface for the hose to form a practically continuous, arcuate supporting surface (FIG. 2), which does not form distinct and separate bends of the hose and thereby not either distinct pumping cells in the hose. In this position of the rollers 7 and 13, which is illustrated in FIG. 2, the liquid output of the pump is equal to zero. The largest liquid output is obtained when the planet wheels 3 are turned with the rollers 7 past the position illustrated in FIG. 3 to a position radially outwards of the axis of the respective planet Wheel, where the space between consecutive rollers is the greatest possible. When the planet wheels 3 are turned with the rollers 7 outwards, the intermediate supporting rollers 13 are moved inwards and thus out of cooperation with the hose.

In order to obtain a larger variation of the output of the pump it is possible according to the second embodiment shown in FIGS. 4 to 6 to amount the rollers 7 on the ends of arms 14, which are fixedly connected with the planet wheels 3 and which can be swung in over the sun wheel 4, as shown in FIG. 6. It will thereby be possible to move the rollers 7 so near to each other as shown in FIG. 6, in which position the rollers 7 themselves form a practically continuous arched support for the hose, so that the volume of the pump cells in this position becomes practically equal to zero. In the radially outwards turned position shown in FIG. the rollers 7 reach a large distance from the shaft 2 and form long pump cells within the hose, which results in a relatively large liquid output of the pump. When the difference between the largest and least possible radius of the rollers is great, the variations of the tension of the hose necessary to obtain a pumping effect at all will be so large, that they must be compensated. A device herefore is shown in FIGS. 4-6, which comprises a slide 16 displaceably guided towards and away from the shaft and supporting the connections 17 for the pump hose 15. This slide is under the action of a spring 18, which is tensioned between a pin 20 on the frame 19 of the pump and a pin 21 mounted on the slide 16 and keeps the hose under the desired tension.

A flexible band 22 having good sliding properties towards the hose and having its ends fixed onto the support 23 for the hose connections 17 on the slide 16, is passed outside the hose around the rollers 7 and limits the displacement of the slide upwards by the spring 18. Instead of a band a thin line can be passed over the rollers 7 besides the hose, preferably in separate guide grooves in said rollers. It is also possible, especially if the changes of liquid output of the pump occur at large time intervals,

to make the slide 16 with the connections 17 adjustable by hand and to provide a stop screw to secure it in the adjusted position. The frame and the slide are then preferably provided with a scale and an index indicating the tension of the hose. A further modification for the adjustment of the tension of the hose 15 is to provide the slide with a tongue extending under the disc 1 and the gear wheels 3 and 4 to the vertical plane passing through the rollers 7, where the tongue has a projection, which is adjustable to such a distance from the shaft, that the projection is just out of the path of motion of the bends of the hose formed by the rollers 7. In FIG. 4 this alternative is shown in mixed lines.

The embodiment illustrated in FIGS. 4 to 6 differs from that illustrated in FIGS. 1 to 3 in a further respect. Instead of providing two plates 6 and 8 rotatable relatively to each other, of which one is connected with the disc 1 and the other with the sun wheel, there is according to FIG. 5 a little gear wheel 24 operable e.g. by a screw driver which meshed with one of the planet wheels 3 and which can be secured by a stop screw 25. The little gear wheel can instead be replaced by selfiocking worm screw meshing with one of the planet wheels. This embodiment is illustrated with one of the planet wheels 3 provided with a scale cooperating with an index 26 on the disc 1.

According to the embodiment illustrated in FIGS. 7 to 9 the means for radially adjusting the space between the rollers 7 and the shaft 2 consists of two parallel discs 27 fixedly mounted on the shaft 2 and having a number of spiral grooves 28 corresponding to the number of rollers on their sides facing each other. Shaft pins 29 for the rollers 7 have their ends guided in the spiral grooves 28. In contact with the inner sides of the discs 27 there are rotatable guide discs 30, which are fixedly connected with each other by means of a tubular hub 31. The guide discs extend a little distance outside the periphery of the discs 27 and cover the edges thereof by a thickened border portion 32. The guide discs have radial slots 33 in a number corresponding to the number of rollers 7. The shaft pins 29 of the rollers 7 extend through the slots 33 into the guide grooves 28. When the guide discs 30 fixedly connected with each other are rotated relative to the discs 27, the shaft pins 29 and thereby also the rollers are moved along the spiral grooves 28 inwards or outwards to the desired position. One of the thickened border portions 32 has preferably a stop screw 34, by which it can be secured in its position relative to the adjacent disc 27. An index 35 on the outside of one of the discs 27 indicates the rotational position of the guide discs 30 on a scale 35a provided on the outside of the adjacent thickened border portion 32. FIG. 8 shows the rollers 7 and their shaft pins 29 in their radially innermost position. Axial pins 36 bridging over the space between the guide discs 30 are fixedly mounted on the guide discs along a circle at a radial distance from the shaft 2 corresponding to the radial distance of the outer periphery of the rollers 7 when these are in their innermost positions. In this position the rollers 7 and the pins 36 form together a practically continuous, annular support for the hose, which thereby is not subjected to the sharp bends necessary for the forming of pump cells within the hose. The pins 36 thus permit a reduction of the liquid output of the pump to zero. When the rollers 7 are moved radially outwards by rotating the guide discs 30 relative to the discs 27, the hose looses its support on the pins 36 and forms closed pump cell between the rollers 7. Even in this embodiment it is possible to obtain a compensation for the tensioning of the hose e.g. by means of the device described in connection with FIGS. 4-6 for the same purpose.

In the embodiment according to FIGS. 10 to 15 the rollers 7 are replaced by balls 37, which are radially movable between grooves 38 on the sides facing each other of discs 39 and 40, which by means of a tubular hub 41 are fixedly connected with the shaft 2 and form the rotatable member. The hub sleeve 41 extends outside one of the discs 40 and has an outer helical groove on which is screwed a nut 42 having a conical tapered end projecting into the space between the discs 39 and 40. On the outside of the nut 42 a counter nut 43 is screwed onto the end of the hub sleeve 41. The pump hose 44 extends from a point above the discs around the balls 37, which are situated in the lower part of the cage formed by the discs 39, 40 and the grooves 38, and keeps the balls pressed radially inwards against the tapered end of the nut 42. The upper balls, which are not maintained by the hose (see FIGS. 13 and 15) are kept in contact with the nut 42 by their own weight. When the nut 42 is displaced along the hub sleeve 41 by relative rotation of these parts, the conical end of the nut is projected more or less into the space between the discs 39 and 40, forcing the balls to take corresponding radial positions. Of the two end positions of the longitudinal motion of the nut and of the radial motion of the balls one is shown in FIGS. 12 and 13 and the other in FIGS. 14 and 15. The discs 39, 40 are between the grooves 38 connected with each other by bridge portions 45, the outwards turned faces of which are in a common cylindric surface, which in the innermost position of the balls shown in FIG. 15 has its inside on a tangent to the balls. The bridges 45 form thus together with the balls a sufficiently uniformly bent supporting surface for the hose to prevent the formation of pumping cells therein. In order to prevent the balls from falling out of the grooves when the hose is removed or when the position of the pump is changed e.g. during transport, the outer ends of the grooves are narrowed by abutments formed by wires 46 placed into peripheral grooves in the outer edges of the discs. An index member 47 mounted on the outside of the disc 40 indicates the screwing position 42 of the nut 42 and thereby the radial position of the balls on a scale 48 marked on the end face of the nut. Since the nut can be screwed in or out several revolutions, it is on the outside provided with a helical groove 49, which cooperates with an index member 47 longitudinally displaceable on a pin, thus giving a raw indication of the screwing position of the nut by reading the spire of groove 49 engaged by the index member 47. For the adjustment of the nut 42, the counter nut 43 is loosened and after the adjustment has been performed, it is retensioned. To reduce the friction between the balls 37, the grooves, the nut and the hose the lower part of the device is preferably emerged in an oil bath 50.

An embodiment, which is based on the same principles but which permits larger radial movements of the balls 37 is shown in FIGS. 16 to 18. In this embodiment two discs 51 are provided with a number of radial slots 52 of such width, that they form guides for the balls 53 placed between such slots. A nut member 55 screwed onto a screw threaded portion of the shaft 2 has radial wings 56 capable of entering the slots 52 and of projecting through them more or less by screwing the nut 55 on the threaded portion 54. The ends of the wings 56 extending through the slots 52 are inclined symmetrically towards the shaft 2, so that the balls are moved outwards by displacing the wings further in through the slots. Since the nut 55 is prevented from rotation relative to the discs 50, 51 by the wings 56 and the slots 52, the discs are rotatably but axially not displaceable on the shaft 2. This device works otherwise in the same manner as that illustrated in FIGS. to 15. Even in the embodiment according to FIGS. 16 to 18 it is possible to provide between the discs bridges of the same kind as the bridges 45 shown in FIGS. 13 and to form at the innermost position of the balls a uniform arcuated support for the hose preventing the forming of pump cells.

The embodiment shown in FIGS. 19 to 21 is based on the same principles as the embodiments according to the embodiments shown in FIGS. 1 to 6, i.e. on the principles of rollers mounted on planet wheels which can be rotated relative to a disc supporting said wheels for changing the liquid output of the pump. This pump according to FIGS. 19 to 21, however, is formed as a differential pump. On each planet wheel there are two diametrically opposed rollers 57 and 58, of which one 57 is axially displaced relative to the other 58. In the embodi ment illustrated there are three planet wheels 59 on each of which one of the rollers 57 is in one plane parallel with the planet wheels, the other rollers 58 being in another plane equally parallel with the planet wheels. The rollers are so arranged on the planet wheels, that when the rollers 57 all are positioned on their largest possible radial distance from the shaft 2, the other rollers 58 are at their shortest possible radial distance from the shaft 2, as shown in FIG. 19. Both ends of the hose 60 are connected to a common inlet 61 and runs, counted from one of the end connections, first over the rollers 57 situated in one plane, thereafter over a return disc 62 and then over the three other rollers 58 situated in the other plane back to the inlet connection 19. In one of the parts of the hose 60 leading to the return disc 62 there is a hose connection to an outlet 63.

Starting from the position of the planet wheels 59 and of the rollers 57 and 58 shown in FIG. 19 and provided the disc 64 supporting the planet Wheels is rotated in the direction of arrow 65, the pump shown in FIG. 19 works in the following manner:

The three rollers 57 situated in one plane at a large radial distance from the axis of rotation of the disc 64 form a pump unit feeding a relatively large quantity of liquid from the inlet 61 in the direction of arrows 66 to the outlet 63. The three other rollers situated in the other plane form a second pump unit which depending on the little radial distance from the axis of rotation feeds a relatively small quantity of liquid from the outlet 63 in the direction of arrows 67 towards the inlet 61. The liquid output at the outlet 63 is then the difference between the quantities fed by each of the pump units in the direction of arrows 66, 67. The liquid output is thus at a maximum when the rollers 57 are in their outmost radial positions and the rollers 58 consequently in the innermost radial positions. By rotation of the planet wheels 59 relative to the disc 64 supporting the same from the position shown in FIG. 19 the rollers 57 are moved nearer the axis of rotation of the disc 64 while the rollers 58 are at the same time moved away from said axis. The quantity of liquid fed by the rollers 57 is reduced while the quantity of liquid fed by the rollers 58 is increased. The difference fed out through the outlet 53 is thereby reduced. During this change of the radial positions of the rollers 57 and 58 a certain length of the hose is transferred from one pump unit to the other over the return disc 62. It is therefore of importance that the hose runs easily over the disc 62 without being squeezed and flattened against it. To ascertain this, the portion of the hose running over the disc 62 is surrounded by an enclosure which is flexible but radially stiffer than the hose, e.g. a sleeve 68 formed by a helical spring. In this device the change of the output quantities of the two pump units cannot be driven farther than to th same value where the differential quantity fed out at 63 is equal to zero because otherwise, since the rollers 57 and 58 are mounted on the same side of the disc 64, the shafts of the rollers 58 situated at a greater distance from the disc 64 would engage the hose part of the other pump unit.

FIGS. 21 and 22, however, show a differential pump in which the feeding quantities of the separate pump units can be adjusted past the point at which they are equal, so that the dilferential quantity fed out at the outlet can be either positive or negative, i.e. the pump can feed the liquid in both directions. In FIGS. 21 and 22 the planet wheels 70 are rotatably mounted on a disc 71 which is fixedly mounted on the rotatable driving shaft 2. The planet wheels 70 are, as stated before, coupled to each other by a sun wheel 72. The planet wheels are rotated by means of a gear wheel meshing with the planet wheel 70 and operable in any known manner, e.g. as previously described in connection with wheel 24 in FIGS. 4 and 6. Each planet wheel 70 has two shaft pins placed at diametrically opposed points of the wheel, of which pins one 74 extends outwards away from the disc 71 and the other 75 projects through an arcuate slot 76 in the disc to the opposite side thereof. Rollers 77 and 78 respectively are mounted onto the ends of the shaft pins 74 and 75. The two hose loops 79 and 80 are passed over the rollers 77 and 78 and are now entirely independent of each other. By rotating the planet wheels half a revolution from the position shown in FIG. 21 the liquid output from the pump unit formed by the rollers 77 is changed from a maximum to a minimum and the output of the pump unit formed by the rollers 78 is changed from a minimum to a maximum. In an intermediate position, in which all the rollers 77 and 78 are on the same radial distance from shaft 2 the outputs are equal and the differential total output is equal to zero. When the output of the pump unit formed by the rollers 78 is larger than that of the pump unit formed by the rollers 77, the flow of liquid is the opposite of that indicated in FIG. 21 by the arrows for the unchanged direction of rotation 81 of the disc 71. The variation of the length of the hose loops due to the change of the radial distance of the rollers 77, 78 is in the device according to FIG. 21 compensated by connecting the ends of the loops 82 and 83 to supports 84, 85 for the hose connections 86, 87 placed on opposite sides of the disc, these supports being mounted on a common slide 89 displaceably guided in the apparatus frame. Hereby the tension in both hose loops 82 and 83 is balanced and when the tension in one of the loops, e.g. 82, is reduced by reducing the radial distance of the corresponding rollers, e.g. 77, the tension in the other 100p, e.g. 83, is simultaneously increased by the increase of radial distance of the corresponding rollers 78, and the slide 89 is thereby automatically displaced until the tensions of the two loops are equalized. In this embodiment one end of each of the hose loops 82 and 83 is connected to a common outlet 90, while the connections for the other ends of the loops are not shown. These other ends can, as in the embodiment shown in FIGS. 19 and be connected to a common inlet 61. The terms outlet and inlet are strictly correct only for the functional position of the apparatus elements shown in FIGS. 21 and 22. In other functional positions the direction of flow of liquid can be changed and outlets become inlets and vice versa.

In all the embodiments hitherto described and illustrated there will be certain pressure pulsations on the outlet side because each time a roller leaves the hose and the squeezng effected by the roller ceases, the elasticity of the hose will again widen it and thereby produce a little pressure reduction pulse. FIG. 23 shows a simple device for compensating for these pressure pulsations.

The driving shaft 2, on which the pump elements are mounted, though not shown in this figure, is driven through a speed reducing gear 91, 92 with a speed ratio corresponding to the number of rollers cooperating with one hose loop. On the shaft 93 or the smaller of the cooperating gear wheels, i.e. the driving gear 92, is fixedly mounted a disc 94 with a radial groove 95. This groove is engaged by a pin 96 excentrically mounted on another disc 97 itself mounted on the motor shaft 98 or on the output shaft of a gear mechanism driven by the motor 99. The motor shaft 98 is adjustable sideways for adjusting the shafts 93 and 98 to a certain desired excentricity. By this device it is possible to impart to the disc 94 and the shaft 93 and thereby to the gear wheel 92 a speed which is accelerated and decelerated once during each revolution. The magnitude of these speed variations is adjustable by displacement of the shafts 93 and 98 relatively to each other. In the embodiment of this device illustrated in FIG. 23 the motor is adjustable sideways in guide slots 100 in the frame 101 and securable in the adjusted position by screws 102. By this device the driving shaft 2 is subjected to speed variations according to the rhythm of the passages of the rollers past a determined point. The device is so adjusted, that the shaft 2 receives a speed acceleration each time a roller leaves the hose loop, whereby the pressure decreasing impulse is compensated by an increased feeding speed of the pump. The balancing of the speed increase in relation to the pressure decreasing pulse can be adjusted by displacement of the shaft 98 relative to the shaft 93.

The invention is not limited to the above described embodiments. First of all it is possible within the scope of the appended claims to produce other combinations of the different elements, eg of the device for adjusting the radial positions of the rollers, of the device for compensating the tension in the hose loop or loops and of the system for obtaining a differential pump effect. As only example herefore an advantageous combination of rollers mounted on arms similar to FIG. 4 to 6 with a differential pump device of the type illustrated in FIGS. 21 and 22 can be named. For such a combination it will be sufficient to let the shafts of the planet wheels extend through disc 71 (FIG. 22) and to provide it with arms 14 with rollers 7 according to FIGS. 4 and 5 on both sides of the disc. Thereby the necessity of arcuate slots 76 according to FIG. 22 is avoided. A differential pump can also be provided with the ball system illustrated in FIGS. 10 to 15 or FIGS. 16 to 18. The hose parts of the differential pump are then passed over two rotatable members mounted on the same shaft, wherein the balls are displaced in opposite direction by oppositely inclined oblique guide surfaces on a common nut member. In differential pumps of the type first described, especially such in which the hose loops are passed over rollers on opposite sides of the rotatable member, the rollers on one side can be rotatable about shafts fixedly mounted on the rotatable member, so that only the rollers cooperating with the hose loop are adjustable to different radial distance from the axis of the rotatable member. For the adjustment and the maintainance of a determined tension in the hose loop or loops it is possible within the scope of the claims to produce an automatic adjustment by mounting the connections for the hose ends on a displaceable member, which is under the influence of a determined force by means of a spring balance or similar mechanism, so that the tension in the hose remains unchanged at any change of the radial adjustment of the rollers as well as at the changes of the length of the hose due to stretching, heat expansion or the like.

What I claim is:

1. A hose pump comprising a flexible elastic hose laid under tension around a number of rollers rotatably mounted on a rotatable member, means for simultaneously changing the radial distance of the rollers from the axis of the rotatable member and means to maintain the tension of the hose approximately unchanged in all possible radial positions of the rollers.

2. A hose pump as claimed in claim 1 in which the rollers are mounted each rotatably and eccentrically on one of a number of planet wheels mounted on the rotatable member and simultaneously rotatable thereon by means of a sun wheel meshing with all the planet wheels for changing the radial distance of the rollers from the axis of the rotatable member and means to maintain the tension of the hose approximately unchanged in all possible radial positions of the rollers.

3. A hose pump as claimed in claim 2 in which two operating discs are mounted for rotation relative to each other in front of the rollers and connected one to the rotatable member and the other to the sun wheel.

4. A hose pump as claimed in claim 2 in which an operating member rotatably mounted on the rotatable member meshes with one of the planet wheels and is securable in the adjusted position.

5. A hose pump as claimed in claim 2 in which the rollers are mounted outside the periphery of the planet wheels on arms fixedly mounted on said planet wheels.

6. A hose pump comprising a flexible elastic hose laid under tension around a number of rollers rotatably mounted on a rotatable member, means for simultaneously changing the radial distance of the rollers from the axis of the rotatable member in which the shafts of the rollers are displaceably guided in radial grooves in one portion of the rotatable member, and in spiral grooves in another portion of the rotatable member, both portions of said rotatable member being rotatable relative to each other for the radial adjustment of the rollers, and means to maintain the tension of the hose approximately unchanged in all possible radial positions of the rollers.

7. A hose pump with a flexible elastic hose laid under tension around a number of rollers rotatably mounted on a rotatable member, said rollers being adjustable on the rotatable member for simultaneously changing their radial distance from the axis of the rotatable member, in which the rollers are guided in radial grooves in the rotatable members and supported radially inwards by inclined surfaces on a member axially adjustable relative to the rotatable member and which comprises means to maintain the tension of the hose approximately unchanged in all possible radial positions of the rollers.

8. A hose pump as claimed in claim 7, in which the rollers are balls, radially guided in grooves in the face to face sides of two discs forming together the rotatable member and radially inwardly supported by inclined surfaces of a member axially adjustable relative to the rotatable member.

9. A hose pump as claimed in claim 7 in which the inclined surfaces are formed by the conically tapering end of a nut axially engaging an axial screw thread on a portion of the rotatable member.

10. A hose pump as claimed in claim 7 in which the inclined surfaces are formed by the chamfered end edges of radial wings on the axially adjustable member extending in radial slots in discs, in which the balls are radially guided.

11. A hose pump with a flexible elastic hose laid under tension around a number of rollers rotatably mounted on a rotatable member, in which the rollers are adjustable on the rotatable member for simultaneous change of their radial distance from the axis of the rotatable member, and in which the rollers in their radial innermost position are so tightly adjacent to each other, that the hose receives a uniform bend without local fiattenings forming pumping cells therein.

12. A hose pump with a flexible elastic hose laid under tension around a number of rollers rotatably mounted on a rotatable member, in which the rollers are adjustable on the rotatable member for simultaneous change of their radial distance from the axis of the rotatable member, and in which the rollers in their radial innermost position are placed between supports forming a uniform circular support, on which the hose receives a uniform bend without local flattenings forming pumping cells therein.

13. A hose pump with a flexible elastic hose laid under tension around a number of rollers rotatably mounted on a rotatable member, in which the rollers are adjustable on the rotatable member for simultaneous change of their radial distance from the axis of the rotatable member and in which the ends of the hose part laid over the rollers is connected to ducts for the pumped liquid by means of connections mounted on a slide radially displaeeable relative to the rotatable member.

14. A hose pump as claimed in claim 13 in which the slide is spring-actuated in the direction of tensioning the hose and is connected to a flexible band laid around the rollers together with the hose to limit the tensioning of the hose.

15. A hose pump with flexible elastic hose parts laid under tension each around one of two series of rollers rotatably mounted on a rotatable member in which the rollers are adjustable on the rotatable member for simultaneous change of the radial distance of the rollers of one series from the axis of the rotatable member in one direction and of the rollers of the other series in the opposite direction, and in which two hose parts connected in series with each other are laid each over one of the series of rollers and at their interconnected ends are connected to a common outlet.

16. A hose pump as claimed in claim 15, in which the two hose parts have their ends on the same side of the rotatable member and at their interconnected ends connected to the common outlet are laid over a return disc.

17. A hose pump as claimed in claim 15, in which the two hose parts have their ends placed on opposite sides of the rotatable member and are connected to hose connecting members on a slide displaceable diametrically of the rotatable member.

18. A hose pump with at least one elastic hose laid under tension around at least one series of rollers rotatably mounted on a rotatable member, in which the rollers are adjustable on the rotatable member for simultaneous change of their radial distance from the axis of rotation of the rotatable member and in which a device for compensating the pressure pulses in the output liquid comprises means for periodically increasing and reducing the rotational speed of the rotatable member during each revolution thereof in synchronism with the times at which the rollers pass the point at which they leave the hose.

19. A hoes pump as claimed in claim 18 in which the rotatable member is driven through a gear mechanism with a gear ratio corresponding to the number of rollers cooperating with one hose part and in which the gear mechanism itself is driven by an excentric pin engaging a radial groove in a driving member adjustable relative to the axis of rotation of the excentric pin.

References Cited UNITED STATES PATENTS 419,461 1/1890 Lee 103149 1,703,361 2/1929 Pohl 103149 2,794,400 6/1957 Bodine 103149 2,885,967 5/1959 Vogel et al. 103149 3,140,666 7/1964 Currie 103149 3,172,367 3/1965 Kling 103149 WILLIAM L. FREEH, Primary Examiner WILBUR I. GOODLIN, Assistant Examiner 

